1. Field of the Invention
The present invention relates to a method for producing new curable resin capable of being cured by the exposure to radiation or heat.
2. Prior Art
Recently there has been a great demand for coating composition having high curing speed. Particularly, the demand for the improvement of printing speed has been increasing along with the development of the printing technology. With the increase in the demand for higher printing speed, the serious demand for the drying speed (curing speed) of printing inks has been more and more growing. In the conventional high speed printing, the printed products are dried up by direct-heating system or by hot-air system as the means for promoting the drying up of the printed products. From 30 to 40% of the solvent contained in the printing inks which are used in such heat-set printing as mentioned above is evaporated by heating to dry the inks. Therefore, a part of the solvent vapor produced in the printing factories, causes pollution problems more often than ever.
Therefore, printing inks of such a type as can be dried up by some means or other without the need for discharging such volatile material as mentioned above, have been desired for by those skilled in the art.
Under these circumstances, there are demands for printing inks which can be dried without being accompanied by the evaporation of solvent, such as ultraviolet ray curing inks or thermosetting type nonsolvent inks. In fact there have already been made proposals for such printing inks.
For example, in Kokai Patent Publication No. 124133/74 it is disclosed that excellent mutual solubility and curing property can be attained when resin obtained by esterifying copolymer resin of dicyclopentadiene and allyl alcohol with (metha-)acrylic acid, is used as curable ink.
However, when the resin disclosed in the above cited Kokai Patent Gazette is used as the curable coating composition, drying speed is not sufficient, and in particular, the resin disclosed in the above cited Kokai Patent Gazette is used as printing ink composition, exposure sensitivity thereof is poor, thus it is not sufficiently adopted for high speed printing so that the printing inks of this type do not meet the original requirement of the printing inks for high speed printing.